JJF 1191-2008 Audiometry Room Acoustic Characteristics Calibration Specification JJF1191-2008 Standard Download Decompression Password: www.bzxz.net
This specification specifies the measurement method for the acoustic characteristics of the audiometry room. This audiometry room is suitable for the audiometric threshold inspection using air conduction headphones, loudspeakers or bone vibrators as sound-generating devices, and using pure tones, FM tones, narrowband noise or recorded language materials as audiometric signals. This specification is also applicable to the test of the acoustic characteristics of the audiometry room for measuring otoacoustic emissions and auditory evoked potentials.

This specification refers to the following documents:
JJG176-2005 Sound Calibrator JJG449-2001
Octave and 1/3 Octave Filters JJF1034-2005
Terms and Definitions of Acoustic Metrology JJF1059-1999
Evaluation and Expression of Uncertainty in Measurement
GB/T3102.7-1993 Acoustic Quantities and Units GB
/T16296-1996 Acoustic Audiometry Methods Part 2: Sound Field Audiometry Using Pure Tone and Narrow-Band Test Signals (eqvISO8253-2:1992) GB
/T16403-1996 "Acoustic audiometry methods - Basic audiometry for pure tone air conduction and bone conduction hearing thresholds" (eqvISO8253-1:1992)
GB/T20441.4-2006 "Measurement microphones - Part 4: Specifications for working standard microphones"
When using this specification, attention should be paid to using the currently valid versions of the above-mentioned references.
1 Scope (1)
2 References (1)
3 Terms and units of measurement (1)
4 Overview (1)
5 Measurement characteristics (2)
5.1 Sound pressure level of background noise (2)
5.2 Sound field characteristics (5)
6 Calibration conditions (6)
6.1 Environmental conditions (6)
6.2 Standard instruments and other equipment (6)
7 Calibration items and calibration methods (7)
7.1 Calibration items (7)
7.2 Calibration methods (7)
8 Expression of calibration results (10)
8.1 Calibration data processing (10)
8.2 Calibration certificate (10)
8.3 Evaluation of the uncertainty of measurement results (10)
9 Recalibration interval (10)
Appendix A Recommended contents of an audiometry room calibration certificate (11)
Appendix B Example of evaluation of the uncertainty of measurement results (14)

National Metrology Technical Specification of the People's Republic of China J3F 1191--2008
Calibration Specification for Acoustic Performanceof Audiometry Rooms
2008 - 03 -24 Issued
2008 - 06 — 24 Implementation
Issued by the General Administration of Quality Supervision, Inspection and Quarantine JJF 1191-2008
Calibration Specification for AcousticPerformance of Audiometry Rooms JJF1191—2008
This specification was approved by the General Administration of Quality Supervision, Inspection and Quarantine on March 24, 2008, and came into effect on June 24, 2008.
Responsible unit: National Acoustic Metrology Technical Committee Drafting unit: Shanghai Institute of Metrology and Testing Technology, China Institute of Metrology
This specification is entrusted to the National Acoustic Metrology Technical Committee for interpretation. Main drafters of this specification:
JJF1191—2008
Gu Jianxiu (Tuhai Institute of Metrology and Testing Technology) Qiu Jianhua (China Institute of Metrology) Participating drafters:
Hua Linhu (Shanghai Institute of Metrology and Testing Technology) Zhang Yi (Shanghai Institute of Metrology and Testing Technology) Chen Jianguo (Shanghai Institute of Metrology and Testing Technology) Chen Jihong (Shanghai Institute of Metrology and Testing Technology) 1
Fan Pu·
References
Technology and measurement units
Overview·
Metrological characteristics
Background noise sound pressure level
Sound field characteristics
6 Calibration conditions
6. 1 Environmental conditions
Standard instruments and other equipment
7 Calibration items and calibration methods
Calibration items
Calibration methods
8 Expression of calibration results·
8.1 Calibration data processing·
Calibration certificate,
8.3 Evaluation of uncertainty in measurement results··9 Recalibration time interval
JJF 1191--2008
Appendix A Recommended contents of audiometry room calibration certificate Appendix B
Example of evaluation of uncertainty in measurement results
1 Scope
JJF 1191-—2008
Calibration specification for acoustic characteristics of audiometry rooms
This specification specifies the measurement method for the acoustic characteristics of the sound field in an audiometry room. This audiometry room is suitable for audiometric examinations using air conduction headphones, loudspeakers or bone vibrators as sound-generating devices, and using pure tones, FM tones, narrowband noise or recorded language materials as audiometric signals. The main purpose is to ensure the accuracy and reproducibility of audiometric results when the subjects are tested in the frequency range of 125Hz~-12.5kHz.
This specification is also applicable to the test of the acoustic characteristics of audiometric rooms for measuring otoacoustic emissions and auditory evoked potentials. 2 References
This specification references the following documents
JJG176-2005 "Sound Calibrator"
JJG449-2001 "Octave and 1/3 Borrowed Band Filters" JJF1031-2005 "Terms and Definitions of Acoustic Metrology" JJF 1059-1999 "Evaluation and Expression of Uncertainty in Measurement" GB/T3102.7--1993 "Quantities and Units of Acoustics" GB/T16296-1996 "Acoustic Audiometry Methods Part 2: Sound Field Audiometry Using Pure Tone and Narrow Band Test Signals" (eqvISO8253-2:1992)
GB/T 16403-1996 "Acoustic Audiometry Methods Pure Tone Air Conduction and Bone Conduction Audiometry Method" (egvISO8253-[1 1992)
GB/T20441.4-2006 "Test Microphone Part 4: Working Standard Microphone Specification" When using this specification, attention should be paid to the use of the current valid version of the above-mentioned referenced documents. 3 Terms and measurement units
In addition to the following terms and definitions, the relevant terms and definitions in JJF 1034-2005 and the quantities and units specified in GB/T3102.7-1993 are applicable to this specification. 3.1 Reference pointreferencepoint
When the subject is in the test position of the sound field, the midpoint of the straight line connecting the two ear canal openings of the subject. 3.2 Reference axisreference axis
The axis perpendicular to the radiation surface of the loudspeaker. For a single radiator or horn loudspeaker, the axis passes through the geometric center of the diaphragm or horn. For a composite sounder, the position of the axis is specified by the manufacturer. 4 Overview
An audiometric room is a room used for testing the hearing of subjects. Its walls are made of sound-absorbing and sound-insulating materials and grids, so that the boundaries can effectively absorb the incident sound. The background noise in the audiometric room should be kept low enough to avoid the background noise in the listening room masking the test sound signal. When using headphones, bone vibrators or field devices to send test sound signals for audio-visual purposes, the allowable value of the background noise should be specified according to different sound generation methods so that it does not affect the hearing test of the subjects. When using a sound device to send test signals for audiometry, the requirements of the sound field in the audiometric room should be considered. 5 Metering characteristics
5,1 Background noise sound pressure level
The background noise sound pressure level in the audiometry room shall not exceed certain specified values ​​that will mask the test signal. The requirements for the background noise sound pressure level in the audiometry room depend on the way the audiometry signal is sent, that is, whether the audiometry signal is sent via headphones, bone vibrators or loudspeakers.
When the audiometry signal is sent by earphones for air conduction audiometry, the maximum background noise sound pressure level allowed in the audiometry room shall not exceed the provisions of Table 1.
Hao1 Maximum allowable background noise sound pressure level (Lm) in 1/3 octave band for air conduction audiometry using typical general-purpose supra-aural headphones Maximum allowable background noise sound pressure level (based on 20uP8)/dB Center frequency of 1/3 octave band/Hz
125H2~-8 000H2
Test pure tone frequency range
250Hz-~8 000Hz
500Hz--8 000Hz
1/3 octave band
Center frequency/Hz
JJF 1191—2008
Table 1 (continued)
Maximum allowable background noise sound pressure level L (based on 20uP8)/dB Test pure tone frequency range
125HzR 000Hz
250Hz-~8 000Hz
500Hz--8 Q00Hz
Note: The data listed in the table are for the minimum hearing threshold level to be measured, which is B. The maximum uncertainty caused by the background noise of the audiometry room is 2 dB. If the maximum uncertainty caused by the allowable background noise is 5 dB, then the value in the table can be increased by 8 dB. If the minimum hearing level to be measured is not 0 dB, the value in Table 1 can be added to the corresponding minimum hearing level to be measured. For example, if the minimum hearing threshold level to be measured is -10 dB, the maximum background noise level allowed in the audiometry room should also be reduced by 10 dB accordingly.
5.1.1 When using a vibrator to send audiometric signals for bone conduction audiometry, the maximum background noise level allowed in the audiometry room should not exceed the specifications in Table 2
Table 2 1/3 octave band allowable background noise sound pressure level (Lm) in the audiometry room when using a bone vibrator for bone conduction audiometry [-um (based on 20μPa)/dB1/3 octave band
1 heart rate/Hz
Test pure tone frequency range
125Hz~8000Hz
250Hz2~8 000Hz
1/3 octave bandwww.bzxz.net
Center frequency/H2
JJF 1191—2008
Table 2 (continued)
Maximum allowable background noise K level Lm (based on 20μPa)/dB Test pure tone frequency range
125Hz--8000Hz
250Hz--800Hz
Note: The data listed in the table are for the minimum listening level to be measured of 0 αB, and the maximum uncertainty caused by the background noise of the audiometry room is 2 dB. If the maximum uncertainty caused by the allowable background noise is 5 dB, the value in the table can be added with 8dB. If the minimum listening level to be measured is not 0dB, the value in Table 2 can be added with the corresponding minimum listening level to be measured. 5.1.2 When a loudspeaker is used to send audiometric signals for audiometric testing, the maximum allowable background noise sound pressure level in the audiometric room should not exceed the prescribed level of 3.
Table 3 Maximum background noise sound pressure level (La yuan) allowed in 1/3 octave band in sound field audiometry Maximum background noise positive level allowed [m (based on 20uPa)/dB Center frequency of 1/3 octave band/Hz
Lowest test frequency
Center frequency of 1/3 octave band/H2
JJF 1191—2008
Table 3 (continued)
Maximum background noise sound pressure level Lx allowed (based on 20uPa)/dB Lowest test frequency
Note 1: The data listed in the table are for the minimum listening level to be measured of 0 dB and the maximum uncertainty caused by the background noise in the audiometry room of 2 dB. If the maximum uncertainty caused by the background noise is allowed to be 5 dB, the value in the table can be added with B, Note 2: When narrow-band noise is used as the test signal, the maximum allowable background noise sound pressure level should be appropriately lower than the value given in Table 3.
If the minimum hearing threshold level to be measured is not UdB, the value in Table 3 can be added with the corresponding minimum hearing level to be measured. 5.2 Sound field characteristics
An audiometric room that meets the following two sound field conditions can meet the usage conditions of most users. s.2.1 Free field
JJF1191—2008
5.2.1.1 The loudspeaker in the audiometric room should be located at the height of the subject's head, with the reference axis passing through the reference point. The distance between the reference point and the loudspeaker reference point should be at least 1m. 5.2.1.2 When the subject and the chair are not present, and other working conditions remain unchanged, the deviation of the sound pressure level at the position 0.15m above, below, left and right of the test point in the plane perpendicular to the reference axis of the loudspeaker from the sound pressure level at the reference point should not exceed ±2 dB for any test signal. 5.2.1.3 When the subject and the chair are not present, the deviation of the sound pressure level of the loudspeaker at 0.10m in front and 0.10m behind the reference point from the theoretical value of the inverse law of sound pressure distance should not exceed ±1 dB. 5.2.2 Diffuse sound field
5.2.2.1 When the subject and the chair are not present, the deviation of the sound pressure level of the omnidirectional microphone at the position 0.15m in front, behind, above, below, left and right of the reference point from the sound pressure level at the reference point should not exceed ±2.5 dB for any test signal. The difference between the sound pressure levels acting on the left and right extreme positions at the same time should not exceed 3 dB. 5.2.2.2 At frequencies of 500 Hz and above, when a directional microphone with a normal-random sensitivity index of 5 dB is used to measure the incident sound, the deviation of the sound pressure levels in the two directions of the maximum and minimum readings at the reference point shall be less than 5 dB. 6 Calibration conditions
6.1 Environmental conditions
Air temperature: (18~28)℃:
Relative humidity: (30~~90)%:
Air pressure: (86~106)Pa.
6.2 Standards and other equipment
1) Measuring amplifier
The frequency range is 100 Hz~~~20 kHz, the frequency response should be better than ±0.2 dB, and the stability during the calibration period should be better than ±0.1 dB.
The short-circuit A-weighted noise of the measuring amplifier should be less than 1.5V. 2) The measurement range of the 1/3 octave sound pressure level of the low noise microphone (including preamplifier) ​​within the frequency range of 20Hz to 20kHz is at least -7dB to 100dB. 3) Strong directional microphone
In the frequency range of 500Hz to 8kHz, the normal-random sensitivity index is ≥5dB. 4) Measuring microphone
The measuring microphone shall meet the requirements of WS2F or WS2D type in GB/T20441.4-2006. 5) 1/3 octave filter
The 1/3 octave bandpass filter shall meet the requirements of Class 1 in JJG4492001. 6) Audio signal generation
The audio signal generator shall have a frequency error of no more than 0.25% within the frequency range of 10Hz to 20kHz, and the total harmonic distortion of the output signal shall be less than 0.5%. The amplitude stability during calibration shall be better than 0.1dB. 7 Power instrument
In the frequency range required for measurement, the frequency response should be better than ±0.2dB, and the stability during calibration should be better than ±0.1 dB.
8) Acoustic calibrator
The acoustic calibrator meets the requirements of Level 1 in JJG 176
Calibration items and calibration methods
Calibration items
JJF 1191—2008
2005.
The calibration items of the acoustic characteristics of the audiometry room are shown in Table 4. Table 4 List of items for calibration of audiometric acoustic characteristics No. Item Name Basic check Sound pressure level of background noise Symmetry of sound field Characteristics of sound field List of items to be calibrated for various types of audiometric rooms Item Name Basic check Sound pressure level of background noise Symmetry of sound field Characteristics of sound field
Type of audiometry room
For pure tone air conduction and bone conduction audiometry
Note, "" represents the calibration item, "_-" represents the item that does not need calibration.
7.2 Calibration method
7.2.1 Audiometry room for pure tone air conduction and bone conduction audiometry is suitable for audiometry rooms that send audiometry signals via air conduction ear and bone vibrator. 7.2.1.1 Basic inspection
Basic inspection Include the following contents:
1) Basic description of the audiometric room to be calibrated,
2) Geometric shape of the interior of the audiometric room:
Free field
Diffuse sound field
3) Sound insulation and vibration isolation structure adopted, form and structural size of sound-absorbing components, sound-absorbing materials, and size of the space after installing the sound-absorbing components;
4) Material of the ground;
5) Structure of the soundproof door and tightness of closure: 6) Sealing condition of the pipe port through which the cable passes, whether there are other reflective objects in the room except the measuring equipment; 7) Indoor ventilation.
The basic inspection results should be recorded and described in detail in the calibration report
7.2.1.2 Background noise sound pressure level
See Figure 1 for the block diagram of the measurement device.
WW Audiometric room
Low noise microphone
JJF 1191-—2008
Measurement of sound pressure level of audio equipment
Figure 1 Block diagram of background noise sound pressure level measurement device 1) Preparation before measurement
1/3 octave
Filter
When measuring the background noise sound pressure level in the audiometry room, the measurement point should be selected at the center of the floor of the audiometry room, with a height of 1.2m, and the measurement should be carried out without the presence of the subject. During the measurement, the soundproof door of the audiometry room should be closed, and the cable duct and other places where sound leaks should be sealed.
2) Measurement method
The background noise measurement conditions in the audiometry room should be the same as those during normal audiometry inspection. If the audiometry inspection is carried out If the ventilation system is in operation, the background noise measurement should be carried out during the operation of the system. Before the measurement, the measurement system is calibrated with an acoustic calibrator, and then the 1/3 borrowed band sound pressure level at the measurement point is measured in turn. The measurement result should not be greater than 5,1, and the requirements of the corresponding clauses in the scheme. 7.2.2 Audiometry room for sound field audiometry
First, determine which sound field characteristics are more suitable for the sound field under consideration based on the sound field conditions of the audiometry room to be tested, and then decide whether to use the metrological characteristics requirements of the free field or the metrological characteristics requirements of the diffuse field. 7.2.2.1 When the audiometry room can be used as a quasi-free field 1) Basic inspection
Same as 7.2.1.1.
2) Background noise sound pressure level
Same as 7.2.1.2.
3) Sound field symmetry
The block diagram of the measurement device is shown in Figure 2.
Signal generator
Power amplifier
Microphone
Measurement amplifier
Figure 2 Block diagram of the audiometric empty sound field symmetry measurement device Placement of test sound source
1/3 octave
Exciter
For the audiometric case, the field source used for the test sound field and its placement should be the same as during the audiometric test. The audiometric source should be located at the center of the ground, at a height of 1.2 m, with the reference axis passing directly through the reference point. The distance between the reference point and the loudspeaker reference point should be at least 1 m. The sound source can be 0° sound incidence (directly on the axis), or 45° or 90° incidence angle. Supplementary test microphone placement
The measurement should be made when the subject and the chair are not present, and other working conditions remain unchanged. The measuring microphone should be placed at the sound source reference point.2 m, the reference axis passes through the reference point, and the distance between the reference point and the loudspeaker reference point is at least 1 m. The sound source can be 0° sound incidence (directly facing the axis), or 45° or 90° incidence angle. The measurement should be carried out when the subject and the chair are not present, and other working conditions remain unchanged. The measurement microphone should be placed at the sound source reference point.
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